In recent years, a thin film technology is widely used to enhance device performances and reduce device sizes. Realizing thin-film devices brings direct merits to users, and in addition, plays an important role from an environmental point of view, such as protection of earth resources and a reduction in power consumption. For the development of the thin film technology, it is essential to respond to demands from industrial aspects, such as increases in efficiency, stability, and productivity of thin film formation and a reduction in cost of the thin film formation. Especially, in order to realize the increase in productivity of the thin film formation, a high-deposition-rate film forming technology is essential. In the film forming method, such as vacuum deposition, sputtering, ion plating, and CVD, an increase in deposition rate is being promoted.
Generally used as a method for continuously mass-producing the thin film is a take-up type thin film forming method. The take-up type thin film forming method is a method for pulling out an elongated substrate, rolled around a pull-out roll, to a transfer system, forming a thin film on the substrate travelling in a transfer process, and taking up the substrate by a take-up roll. By combining the take-up type thin film forming method with, for example, a high-deposition-rate film forming method, such as vacuum deposition using an electron beam, the thin film can be continuously mass-produced with high productivity.
However, in a case where the take-up type thin film forming method and the vacuum deposition are combined as above, radiation heat from an evaporation source and heat energy of deposition particles are applied to the substrate. This increases the temperature of the substrate to cause the deformation, meltdown, or the like of the substrate. Moreover, even in a case where the take-up type thin film forming method is combined with the other film forming method whose heat source is different from the above, heat load is applied to the substrate during the film formation. To prevent the deformation, meltdown, or the like of the substrate by such heat load, the substrate needs to be cooled down in the take-up type thin film forming method.
Widely used as a method for cooling down the substrate is a method for providing the substrate along a cylindrical can disposed on a passage of the transfer system and transferring the heat of the substrate to the cylindrical can. In accordance with this cooling method, by securing thermal contact between the substrate and the cylindrical can, the heat of the substrate can be transferred to the cylindrical can having a high heat capacity. With this, the temperature increase of the substrate can be suppressed, and the temperature of the substrate can be kept at a specific temperature. Reported is that, for example, a gas cooling method for introducing a gas into between the substrate and the cylindrical can is used under a vacuum atmosphere (see PTL 1, for example). In accordance with this method, the thermal contact between the substrate and the cylindrical can can be secured via the gas, and the temperature increase of the substrate can be suppressed.
Instead of the cylindrical can, a cooling belt may be used as means for cooling down the substrate. For example, in the case of the thin film forming method by oblique incidence, forming the film with the substrate moving linearly is advantageous from a viewpoint of the use efficiency of a film forming material. In this case, it is effective to use the cooling belt as the substrate cooling means. In a thin film forming device using a belt for transferring and cooling a substrate material, another cooling belt is further provided inside the cooling belt, or a cooling mechanism using a liquid cooling medium is provided inside the cooling belt. With this, cooling efficiency can be improved, and the temperature increase of the substrate material can be suppressed (see PTL 2, for example).